If you use your PC's USB port to deliver power supply to experimental electronic circuits (such as single board computer projects), then you are immediately at risk of damaging the PCs USB port.
USB devices should draw no more than 500 mA (0.5 A) from a USB 2 port or 900 mA (0.9A) from a USB 3 power delivery port.
As far as I am aware, the USB specification does not include circuit protection against over-voltage or short circuits, etc. Far safer to use an independent power supply if you intend to power experimental electronic curcuits.